The Philip Allan Review magazines are good sources of articles perfect for IGCSE and IB students.
The archive interface isn't very efficient, but it's worth struggling with to get to the material.
To access the archive, go to https://www.uwcsea.edu.sg/philipallan
You will be prompted to log into the school website first.
Enter your search terms -- and select which titles to search.
Scientific Research Publishing (SCIRP) is one of the largest Open Access journal publishers. It is currently publishing more than 200 open access,online, peer-reviewed journals covering a wide range of academic disciplines. 
Sample article, searching for "polymers"....
